A pressure governor is provided with a pump capacity regulator which is controllable by means of a hydraulic motor operator which can be driven by alternative pressurization and depressurization of a driving chamber for carrying out the movements for the opposite changes of the displaced volume of the variable displacement pump. Typically a pressure regulated valve is designed for controlling the pressurization and depressurization of this pressure driving chamber, which, regulated by the initial pressure of the pump or a pressure proportional to this, from a minimum pressure determined by a minimum restoring force of a restoring element, e.g. a spring, releases an initial pressure together with the control pressure coupled into its control chamber, by which the driving pressure chamber of the motor operator is pressurized.
Such pressure governors are well known. They comprise a valve driven by the initial pressure of the variable displacement pump designed, for example, as a proportional valve which, with increasing initial pressure of the variable displacement pump, is increasingly pushed against the restoring force of a valve spring into the functional position providing the activation of the actuating drive, whereby in the stationary position of the pressure control the initial pressure of the variable displacement pump is determined by the preset initial tension of the valve spring. This type of control which may be superimposed by a volume flow control, which--on a lower pressure level than the maximum level determined by the pressure regulating valve--provides a constant control of the volume flow of the high-pressure pump. It has, however, the disadvantage that in the starting situations of a hydraulic power consumer which, in the stationary position of its movements, needs a relatively high operating pressure level. Thus, strong pressure shocks may occur which promote wear and are combined with considerable noise, because in the starting situation the pressure governor is adjusted to a maximum capacity volume of the variable displacement pump which is reduced only after pumping starts. Comparable with this is also the situation that the consumer or a driving cylinder thereof is blocked, because then also the initial pressure of the variable displacement pump increases very fast--like a shock--to the value given by the pressure limit. These problems are particularly aggravating with hydraulic power consumers which are driven by linear cylinders or hydraulic oscillating motors carrying out periodic oscillating movements.